NETWORK ENGINEER BLOG

Tips and Reviews for Engineers

OSPF で Neighbor を確立できない原因

OSPF で Neighbor を確立できない要因は様々ですが、その中に「パラメータのミスマッチ」があります。
Neighbor を確立するために、対向で合わせる必要があるパラメータをいくつか紹介致します。

Network Type

Cisco は下記の Network type をサポートしています。

  • Non Broadcast Multi Access (NBMA) - RFC 2328 Standard
  • Broadcast - Cisco Proprietary
  • Point-to-Multipoint - RFC Standard
  • Point-to-Multipoint, Non-Broadcast - Cisco Proprietary
  • Point-to-Point - Cisco Standard
  • Loopback - Cisco Standard

Network Type は show ip ospf interface コマンドで確認します。

Router#show ip ospf interface
GigabitEthernet2 is up, line protocol is up
  Internet Address 100.64.1.2/24, Area 0, Attached via Network Statement
  Process ID 1, Router ID 100.64.1.2, Network Type NON_BROADCAST, Cost: 1
  Topology-MTID    Cost    Disabled    Shutdown      Topology Name
        0           1         no          no            Base
  Transmit Delay is 1 sec, State DR, Priority 1
  Designated Router (ID) 100.64.1.2, Interface address 100.64.1.2
  No backup designated router on this network
  Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
    oob-resync timeout 120
    Hello due in 00:00:06
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Can be protected by per-prefix Loop-Free FastReroute
  Can be used for per-prefix Loop-Free FastReroute repair paths
  Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 0, maximum is 2
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 0, Adjacent neighbor count is 0
  Suppress hello for 0 neighbor(s)
OSPF Area Type

Cisco は下記の Area Type をサポートしています。

  • Backbone area (area 0)
  • Standard area
  • Stub area
  • Totally stubby area
  • Not-so-stubby area (NSSA)

Area Type は show ip ospf コマンドで確認します。

Router#show ip ospf
 Routing Process "ospf 1" with ID 100.64.1.2
 Start time: 02:42:47.473, Time elapsed: 04:13:37.263
 Supports only single TOS(TOS0) routes
 Supports opaque LSA
 Supports Link-local Signaling (LLS)
 Supports area transit capability
 Supports NSSA (compatible with RFC 3101)
 Event-log enabled, Maximum number of events: 1000, Mode: cyclic
 Router is not originating router-LSAs with maximum metric
 Initial SPF schedule delay 5000 msecs
 Minimum hold time between two consecutive SPFs 10000 msecs
 Maximum wait time between two consecutive SPFs 10000 msecs
 Incremental-SPF disabled
 Minimum LSA interval 5 secs
 Minimum LSA arrival 1000 msecs
 LSA group pacing timer 240 secs
 Interface flood pacing timer 33 msecs
 Retransmission pacing timer 66 msecs
 Number of external LSA 0. Checksum Sum 0x000000
 Number of opaque AS LSA 0. Checksum Sum 0x000000
 Number of DCbitless external and opaque AS LSA 0
 Number of DoNotAge external and opaque AS LSA 0
 Number of areas in this router is 1. 0 normal 1 stub 0 nssa
 Number of areas transit capable is 0
 External flood list length 0
 IETF NSF helper support enabled
 Cisco NSF helper support enabled
 Reference bandwidth unit is 100 mbps
    Area 1
        Number of interfaces in this area is 1
        It is a stub area
        Area has no authentication
        SPF algorithm last executed 00:14:46.179 ago
        SPF algorithm executed 3 times
        Area ranges are
        Number of LSA 3. Checksum Sum 0x0095DE
        Number of opaque link LSA 0. Checksum Sum 0x000000
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0

Area Type が対向で異なる場合、debug ip ospf hello で下記エラーを検出します。

OSPF-1 HELLO Gi2: Rcv hello from 100.64.1.1 area 1 100.64.1.1
OSPF-1 HELLO Gi2: Hello from 100.64.1.1 with mismatched NSSA option bit
Hello/Dead Interval

Hello/Dead Interval のデフォルトは下記のとおりです。

  • Non Broadcast Multi Access (NBMA) - Hello 30sec / Dead 120sec
  • Broadcast- Hello 10sec / Dead 40sec
  • Point-to-Multipoint - Hello 30sec / Dead 120sec
  • Point-to-Multipoint, Non-Broadcast - Hello 30sec / Dead 120sec
  • Point-to-Point - Hello 10sec / Dead 40sec
  • Loopback - N/A|

Hello/Dead Interval は show ip ospf interface コマンドで確認します。

Router#show ip ospf interface
GigabitEthernet2 is up, line protocol is up
  Internet Address 100.64.1.2/24, Area 1, Attached via Network Statement
  Process ID 1, Router ID 100.64.1.2, Network Type BROADCAST, Cost: 1
  Topology-MTID    Cost    Disabled    Shutdown      Topology Name
        0           1         no          no            Base
  Transmit Delay is 1 sec, State DR, Priority 1
  Designated Router (ID) 100.64.1.2, Interface address 100.64.1.2
  No backup designated router on this network
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:08
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Can be protected by per-prefix Loop-Free FastReroute
  Can be used for per-prefix Loop-Free FastReroute repair paths
  Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 0, maximum is 1
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 0, Adjacent neighbor count is 0
  Suppress hello for 0 neighbor(s)

Hello/Dead Interval が対向で異なる場合、debug ip ospf hello で下記エラーを検出します。

OSPF-1 HELLO Gi2: Rcv hello from 100.64.1.1 area 1 100.64.1.1
OSPF-1 HELLO Gi2: Mismatched hello parameters from 100.64.1.1
OSPF-1 HELLO Gi2: Dead R 30 C 40, Hello R 10 C 10 Mask R 255.255.255.0 C 255.255.255.0